It is not the first time women journalists working in the area have been attacked - last year US correspondent Lara Logan was sexually assaulted in the square while working for CBS television.

Writing on her blog, Ms Smith said: "I have been forced to leave Cairo prematurely following a horrific sexual and physical attack in Tahrir Square."

The student, who went to school in Budmouth, Dorset, was walking near the square with two male friends when the atmosphere of "jubilation, excitement and happiness" changed "in a split second".

She said: "Men had been groping me for a while, but suddenly, something shifted. I found myself being dragged from my male friend, groped all over, with increasing force and aggression. I screamed. I could see what was happening and I saw that I was powerless to stop it. I couldn't believe I had got into this situation."

She described how "hundreds of men" dragged her away and ripped off her clothes.

Ms Smith said: "I was stripped naked. Their insatiable appetite to hurt me heightened. These men, hundreds of them, had turned from humans to animals. So many men. All I could see was leering faces, more and more faces sneering and jeering as I was tossed around like fresh meat among starving lions."

She described how "a small minority of men" tried to protect her and sheltered her in a tent before she was smuggled away disguised in a burka and taken to hospital.

Ms Smith said she is "determined" to return to Egypt to complete her work, adding: "I have so much to say, and I will say it, in time."